<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
    <style>
      #box {
        width: 200px;
        height: 200px;
        background-color: antiquewhite;
      }
    </style>
  </head>
  <body>
    <div id="box"></div>
    <button id="btn">提交</button>

    <script>
      var btn = document.getElementById('btn');
      var box = document.getElementById('box');
      var flag = true;
      btn.onclick = function () {
        if (flag) {
          console.log(flag);
          box.style.display = 'none';
        } else {
          box.style.display = '';
        }
        flag = !flag;
      };
    </script>
  </body>
</html>
